Sp1 phosphorylation induced by serum stimulates the human alpha 2 (I) collagen gene expression

Serum has been known to stimulate collagen production by dermal fibroblasts . As part of an ongoing study of the molecular mechanisms of collagen produ ction, we have investigated transcriptional regulation of the human alpha2( I) collagen gene by serum in human dermal fibroblasts. Serum responsive ele ments were mapped by deletion analysis between by -353 and -264, and betwee n -148 and -108 in the alpha2(I) collagen promoter. Further functional anal ysis of the alpha2(I) collagen promoter containing various substitution mut ations revealed that serum stimulation of this promoter is mediated equally by a GC-rich region located between by -303 and -271 and by the TCCTCC mot if located between by -123 and -128, both of which constitute binding sites for transcription factor Sp1 and Sp3. No differences were observed in elec trophoretic mobility shift assays between unstimulated and serum stimulated fibroblasts. The Sp1 inhibitor mithramycin blocked stimulation of the alph a2(I) collagen promoter activity by serum. Furthermore, immunoprecipitation analysis showed that serum stimulation increased Sp1 phosphorylation. In c onclusion, this study characterized response elements that mediate serum st imulation of the human alpha2(I) collagen promoter and suggests that serum stimulation was mediated via Sp1/Sp3 binding sites in this promoter.